Blog

When to Plant Comfrey in Stanislaus County, CA

Stanislaus County, California Zone 9b May

What to do in May

A quick May briefing for Stanislaus County, California gardeners — what's urgent, what's next, and what can wait.

Avg. last frost February 24
Avg. first frost November 28
Soil temp (4") 71°F
Watering Critical
Pest pressure High
Daylight 14 hrs
  1. Basket week: comfrey

    This is the payoff month. Bring a basket, bring a friend, and get into the beds.

To set up a strong June, finish these tasks
  • First harvests: comfrey

Instant PDF download. No spam, unsubscribe any time.

Comfrey is a vigorous perennial herb valued as a dynamic accumulator of nutrients. Its leaves make excellent mulch, compost activator, and liquid fertilizer.

Stanislaus County, California is in USDA Zone 9b. The average last spring frost is February 24 and the first fall frost is November 28, giving you a growing season of approximately 277 days.

At an elevation of 2,887 feet, Stanislaus County receives approximately 15.2 inches of rainfall annually with predominantly loam soil. Summer highs average 94°F, providing good warmth for Comfrey during the growing season. With low rainfall, drip irrigation is essential for growing Comfrey successfully. Mulch heavily to conserve soil moisture.

Stanislaus County, CA (Zone 9b) Year-round
277 days
Last Spring Frost February 24
277 growing days
First Fall Frost November 28

Stanislaus County Soil Profile

Soil Type

Loam

Soil pH

6.5-7.7

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (149 days to spare)
Transplant: Feb 13 🍅 Harvest: Apr 17 – Jun 26
Recommended (50%) ✓ Fits season (137 days to spare)
Transplant: Mar 3 🍅 Harvest: May 5 – Jul 14
Safe Start (90%) ✓ Fits season (102 days to spare)
Transplant: Apr 25 🍅 Harvest: Jun 27 – Sep 5

Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.

Soil Compatibility in Stanislaus County

How your county's soil matches Comfrey's growing requirements.

Soil pH

Your soil pH (6.5–7.7) is more alkaline than Comfrey prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

The loam soil in Stanislaus County is excellent for Comfrey — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is moderate (2.6%). Annual compost additions will help Comfrey.

How to Plant Comfrey

0.5"
Planting Depth
8"
Between Plants
12"
Between Rows

Succession Planting Comfrey

5
successive plantings in your 277-day season

Sow every 6.9 weeks. Last sowing by Aug 30 to harvest before frost.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.2″/week
You supply
0.9″/week
Watering frequency 2-3 times/week
Season total 2,287 gal / 100 sq ft
Drought risk

Water stress score is 8/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Comfrey

Comfrey needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.

Month Comfrey Needs Rainfall You Supplement Action
Jan 3.1" 0" ❄️ Dormant
Feb 4.3" 3.5" 0.8" 💧 Light watering
Mar 4.3" 2.1" 2.2" 🚿 Regular watering
Apr 4.3" 1.3" 3" 🚿 Regular watering
May 4.3" 0.5" 3.8" 🚿 Regular watering
Jun 4.3" 0.1" 4.2" 🚿 Regular watering
Jul 4.3" 0" 4.3" 🚿 Regular watering
Aug 4.3" 0" 4.3" 🚿 Regular watering
Sep 4.3" 0.2" 4.1" 🚿 Regular watering
Oct 4.3" 0.7" 3.6" 🚿 Regular watering
Nov 4.3" 1.5" 2.8" 🚿 Regular watering
Dec 2.2" 0" ❄️ Dormant

Water needs are for active growing months only (Feb–Nov in Stanislaus County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Comfrey Heat Requirements (GDD)

What are Growing Degree Days (GDD)?

Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.

Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.

Comfrey needs ~1,538 GDD — county provides 5,699 GDD Excellent fit

Comfrey Planting Timeline — Stanislaus County, CA

Comfrey Planting Calendar

Activity When Date Range
Transplant Outdoors March 3 Mar 3 – Mar 17
Harvest May 5 May 5 – Jul 14

Plant 0.5" deep · 8" apart · Rows 12" apart

Month-by-Month Timeline

MonthActivities
January
February
March Transplant Outdoors
April
May Harvest
June Harvest
July Harvest
August
September
October
November
December

Growing Conditions

☀️ Sun

Partial Shade (3-6 hours)

💧 Water

1"/week · 2-3 times/week

📅 Days to Maturity

60–90 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 9b

📆 Growing Season

277 days in Stanislaus County

Growing Tips for Comfrey in Stanislaus County

Direct sow Comfrey outdoors after February 24 in Stanislaus County when soil has warmed and frost danger has passed.

Stanislaus County receives only 15" of rain annually. Comfrey needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.

General growing tips

Plant root cuttings 2 inches deep. Choose Bocking 14 variety to prevent self-seeding. Cut leaves 3-4 times per season for mulch or compost. Avoid planting near pathways as it spreads.

Companion Planting

Good Companions

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Comfrey in Stanislaus County, CA?

Stanislaus County is in Zone 9b with an average last frost of February 24. Plan your Comfrey planting based on this frost date — see the calendar above for exact timing.

What planting zone is Stanislaus County, CA?

Stanislaus County, California is in USDA Hardiness Zone 9b. The average last spring frost is February 24 and first fall frost is November 28.

🌱

Your Stanislaus County Garden Planner — Free

A 24-page printable planner built for Stanislaus County (Zone 9b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.

Instant PDF download. No spam, unsubscribe any time.

Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Stanislaus County, CA. Local conditions may vary. Last updated: May 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.